Method of constructing a plate type heat exchanger



Dec. 26, 1967 G, UTT

METHOD OF CONSTRUCTING A PLATE TYPE HEAT EXCHANGER 2 Sheets-Sheet 1 Filed June 28, 1965 INVENTOR.

ALAN G. BUTT /v%/r o V W ATTORNEYS A. G. BUTT Dec. 26, 1967 METHOD OF GONSTRUGTING A PLATE TYPE HEAT EXCHANGER Filed June 28, 1965 2 Sheets-Sheet 2 1 N VENTOR.

ALAN G. BUTT ATTORNEYS United States Patent 3,359,616 METHOD 0F CONSTRUCTING A PLATE TYPE HEAT EXCHANGER Alan G. Butt, La Crosse, Wis, assignor to The Trane Company, La Crosse, Wis., a corporation of Wisconsin Filed June 28, 1965, Ser. No. 467,623 13 Claims. (Cl. 29-157.3)

This invention relates to plate type heat exchangers. More particularly, this invention relates to a method of constructing plate type heat exchangers with extended heat transfer packing in only some of the passageways thereof.

Heat exchangers of the type to which this invention pertains are comprised of a plurality of metallic plates which are disposed in face-to-face spaced relationship. The spaces between the plates form the heat exchange passageways and heat exchange is by conduction through the plates. In order to improve heat transfer between the heat exchange fluid and the plate, it is commonplace to include within the passageways an extended heat transfer packing which may have any of several different configurations including that of a corrugated metallic sheet. The heat exchanger of the instant invention utilizes a packing which extends from one plate of a passageway to the other plate of the passageway thereby providing structural continuity to the heat exchanger core in addition to improving heat transfer when the packing is bonded to the plates. This invention relates to such heat exchangers wherein the packing is bonded to the plates as by brazing the exchanger in a furnace or bath.

In heat exchangers of the aforementioned type it may be unnecessary to include packing in both heat exchange streams. This may be the case when a liquid and a gas are heat exchanged; the liquid stream usually requiring less heat transfer surface than the gaseous stream. Or, it may be desirable to leave extensive packing out of certain passages to prevent the undesirable accumulation of certain particles generated or carried by one of the heat exchange fluids. Thus it is desirable for a variety of reasons to construct a brazed plate type heat exchanger wherein wall-to-wall packing is provided in passageways associated with only one of the heat exchange fluids.

However, when packing was eliminated from the passageways of one of the streams, it was found that the overall heat transfer coefiicient for the heat exchanger was lower than anticipated.

After due consideration, I further discovered that the elimination of the wall-to-wall heat transfer packing from some of the passages of such heat exchangers resulted in a separation between the packing and plates in other passages. In other words, the brazing bond between the plates and the packing was not complete.

This incontinuity I have found can be eliminated or at least materially mitigated by my novel method of constructing such heat exchanger cores.

It is therefore an object of this invention to provide a method of constructing a heat exchanger core having wall-to-wall heat transfer packing in only some of the passageways thereof.

Another object is to provide a method of constructing a heat exchange core having wall-to-wall heat transfer packing in only some of the passageways thereof wherein said heat transfer packing is provided with an effective structural and thermal conducting bond to the walls of said other passageways.

A further object of this invention is to provide in the construction of a brazed plate type heat exchanger with wall-to-wall packing in only certain passageways thereof a method of temporarily supporting the walls of said certain passageways to minimize warpage of said walls. This method includes the step of temporarily supporting the plates of the passages containing packing during the brazing steps to prevent the plates from warping away from the packing.

The instant invention pertains to the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, and particularly pertains to the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing a sheet of porous material; forming a corrugated spacer member by corrugating said porous material with undulations of a form having crests which define edges; providing within said second passageway said corrugated spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; immersing said exchanger in a bath of molten salt and heating said exchanger in said salt bath to a temperature sufficiently high to allow said brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said edges of said spacer member; isolating said spacer member from said brazing alloy to avoid bonding with said spacer member; withdrawing said exchanger from said salt bath; draining molten salt from said second passageway through the pores of said spacer; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; progressively collapsing undulations of said corrugated spacer member and withdrawing said member from one of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

Further the invention includes the method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing sheets of porous material; forming corrugated spacer members by corrugating said porous material with undulations of a form having crests which define edges; providing said assemblage of elements with corrugated spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said edges of said spacer members; providing means to prevent said brazing alloy from bonding said spacer members to said plates; immersing said assemblage of elements in a bath of molten salt; heating said assemblage of elements in said bath to a temperature sufiiciently high to melt said brazing alloy; withdrawing said assemblage of elements from said bath; draining molten salt from said second passageways through the pores of said spacer members; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and progressively collapsing the undulations of said corrugated spacer members and withdrawing said spacer members from said assemblage of elements through said openings.

Other objects and advantages will become apparent as this specification proceeds to describe the invention with reference to the accompanying drawing in which:

FIGURE 1 illustrates the step of forming a porous spacer member to be temporarily installed in an assemblage of elements to be formed into a heat exchanger core;

FIGURE 2 is a perspective view of the assemblage of heat exchanger elements having portions thereof broken away to disclose details thereof;

FIGURE 3 illustrates the steps of immersing the assemblage into a bath of molten salt flux and heating the assemblage thereby brazing the heat exchanger packing to the plates thereof;

FIGURE 4 is an enlarged section taken at line 44 of FIGURE 3 showing how the porous spacer members support the plates against the packing so as to permit molten brazing alloy to form a strong and complete bond between the plates and the packing;

FIGURE 5 illustrates the steps of withdrawing the assemblage from the bath, draining the molten salt flux from the assemblage and cooling the assemblage to allow the brazing alloy to solidify; and

FIGURE 6 is a perspective view which illustrates the steps of collapsing and withdrawing the temporary spacer members from the brazed heat exchanger core and the addition of inlet and outlet headers to certain of the passageways thereof.

Now referring to the drawing it will be seen that FIG- URE 1 schematically illustrates one method of forming a temporary spacer for construction of a heat exchanger in accordance with the principles of the instant invention. A metallic sheet 10 such as aluminum which has been provided with a plurality of through-going holes 12 may be corrugated by passage between a pair of rollers 14 which are properly contoured to form a corrugated spacer member 16 of the desired configuration. It is desirous for reasons herein-after discussed that the individual undulations of the spacer member 1 5 be of such a form that upon placing the corrugated spacer against a fiat plate, the outer edgesor crests of the spacer member contact the plate in a plurality of lines. This, as will be later explained, facilitates the removal of the spacer from the heat exchanger core when it is no longer needed. A spacer member having V-shaped or plaited undulations is preferred, however, a spacer having sinusoidal crosssection is accept-able. The V-shaped undulations have the added advantage of providing a greater strength to weight ratio.

The components of the heat exchanger core are assembled as illustrated in FIGURE 2. The assemblage 18 comprises a plurality of similar rectangular aluminum plates 20 which are arranged in superposed spaced generally parallel relationship defining the sidewalls of a plurality of fluid passageways therebetween. A group of first passageways 22 is arranged for passage of a first heat exchange medium in heat exchange relation with a second heat exchange medium in a group of second passageways 24 via thermal conductivity through plates 20.

Each passageway 22 has an end closing bar 26 extending along the shorter margins at each end thereof for sealably connecting between the plates 20. Similarly each passageway 22 has a side closing bar 28 extending along each of the longer margins for sealably connecting the plates 20 thereof. Bars '26 and 28 in conjunction with plates 20 define passageways 22 when subsequently sealingly brazed in position. Bars 28 on the back side (FIG- URE 2) of the passageways 22 terminate short of one end thereof thus forming inlet openings 3% for receiving the first heat exchange medium. Bars 23 on the front side (FIGURE 2) of the passageways 22 terminate short of the other end thereof thus forming outlet openings 32 for discharging the first heat exchange fluid.

Within each passageway 22 is a heat transfer packing 34 comprised of corrugated aluminum sheets which may be perforated if desired. The packing extends from Wallto-wall, i.e. from one plate 20 to the other plate 20 of the passageway, in which it is disposed. The crests of the corrugated packing 34 may be arranged parallel with the closing bars 28. A section of heat transfer packing 36 having similar corrugations arranged with the crests thereof extending parallel to the end closing bars 26 may be arranged adjacent inlet openings 30, and outlet openings 32 to facilitate distribution and collection of the first heat exchange medium to and from the passageways 22 respectively.

Each of passageways 24 has a side closing bar 38 extending along the longer margins of the passageways 24 for connecting between the plates 20 thereof. The ends of passageways 24 are left open thereby defining inlet and outlet openings 39 for passage of the second heat exchange medium.

The closing bars, plates and packing hereto-fore described are, during a step subsequent to their assembly, brazed in the positions described by subjecting the entire assemblage of elements to a temperature sufficiently high to melt a brazing alloy and allow it to flow between the joints of these elements. The brazing alloy may be applied to the assemblage of elements in different ways. For example, plates 20 and/or closing bars 26, 2S and 38 may be cl-ad with a brazing alloy on those surfaces to be braze bonded. Or, a separate brazing alloy foil may be interposed within the joints of the assemblage. Further, it is also possible in the alternative to apply the brazing alloy to the desired parts in the form of an emulsion which may be coated on the areas to be joined. All of these methods are known to the art of brazing plate type heat exchanger cores and no further detailed descript-ion will therefore be given. However, it should be mentioned that the brazing alloy applied in any one of these ways may upon melting tend to flow into areas in which it is not desired. This will be discussed in greater detail at a later point in this specification.

In order to minimize warpage of and to temporarily support plates 20 in contiguous relationship with packing 34 and 36 during the subsequent brazing step, passages 24- are filled with one or more corrugated spacer members 16 heretofore described. The corrugated spacer member is of sufiicient thickness that its undulations extend substantially from one plate 20 to the other plate 20 within the pass-ages 24 thereby supporting the plates.

It will be understood that plates 20 are thus supported on one side by packing and on the other side by spacer members.

Since the spacer members 15 are placed in the assemblage of elements only temporarily and must subsequent to the brazing step be removed, a means is provided in the assemblage to prevent the brazing alloy from flowing into areas where it might permanently bond the spacer to adjacent elements. This can be accomplished by facing the sides of the spacer member with a paper insulator 40 or the like which will inhibit the flow of molten brazing alloy. If an aluminum brazing alloy is used, a coating of a refractory oxide such as the zirconium oxide containing compound sold under the trade name of Tam Zirconite by National Lead Company may be successfully employed as the insulator. Such insulators also prevent pressure welding of the spacer members 16 to the plates 20 which may otherwise occur at brazing temperatures even in the absence of a brazing alloy.

The aforementioned elements are assembled in any order to form the assemblage shown in FIGURE 2. A jig or other fixture (not shown) may be applied externally to the assemblage to support the assemblage during the sub; sequent steps.

The assemblage is then immersed into a bath 42 containing a molten salt flux 44 as illustrated in FIGURE 3. The assemblage is heated by the flux to a temperature sufficiently high to melt the brazing alloy and allow it to flow within all the joints to be bonded. This temperature is also sufficiently high to permit plates 20 to warp if not adequately supported. It should be understood that the molten brazing alloy cannot always bridge between the packing and the areas of the plates which have warped away from the packing. Such areas become structural discontinuities within the heat exchanger core and often materially weaken the core. Further the thermal conducting brazed link between packing and plate is short circuited in these areas resulting in a loss of efiiciency of the heat exchanger.

However, in the instant method of constructing a brazed plate type heat exchanger, passages 24, as aforementioned, are filled with a temporary support member 16 for supporting the plates against the packing, thus preventing the plates from warping away from the packing. FIGURE 4 shows how plates 20 within the core are supported from both sides by the packing 34 and spacer members 16. Under the procedure of this invention the brazing alloy as shown at 35 easily bridges between the plates and packing resulting in a substantially complete and structurally flawless thermal conducting union.

During the time when the brazing alloy is in a molten state, spacer members 16 are isolated from the molten brazing alloy by the barrier formed by paper insulators 40 which surround the spacer members 16 thereby preventing bonding of the spacer members 16 to the heat exchanger elements.

After the brazing alloy has melted sufficiently, the heat exchanger assembly 18 is withdrawn from the bath 42 as shown in FIGURE 5. The assembly is disposed in such position that the longitudinal and transverse axes thereof make about a 20 angle with the horizontal. In this position the molten flux 44 is allowed to drain from passage openings 32 and 39. It will be understood that holes 12 in spacers 16 function as drains for flux 44 which may otherwise be trapped within the passages 24.

Subsequent to the removal from bath 42, assembly 18 is allowed to cool to solidify the brazing alloy thereby forming a strong thermal conducting bond at the desired locations. Residual solidified flux may be washed from the core as desired.

After cooling the assembly 18, the spacer members 16 are grasped at one end thereof and pulled through the opening 39 of the passages 24. As the spacer is pulled it progressively unfolds and collapses away from the adjacent plates as illustrated in FIGURE 6. Since the undulations of the spacer member progressively collapse, only a small force is required to withdraw the member thus avoiding tearing of the spacer member sheet material. The particular shape of the undulations of the spacer 16 as aforedescribed further facalitates collapsing of the spacer. Thus it will be seen that the support rendering edges of the spacer do not present large areas that would cause a drag on the spacer as it is withdrawn. As spacer 16 is withdrawn, each support rendering edge will simply pivot away from the adjacent plate and offer no further resistance to removal.

After having removed the spacer members 16, the assembly may again be flushed with water or other solvent for removing additional deposits of flux remaining in the heat exchanger core.

Inlet and outlet headers 46 and 48 may be welded or locally brazed at the sides of the heat exchanger core adjacent inlet openings 22 and outlet openings 32.

Thus it will be seen that the aforedescribed method of constructing a brazed plate type heat exchange core permits certain passages to be provided with a wall-to-wall packing provided with a substantially flawless bond while certain other adjoining passages are without such wallto-wall packing. This construction method thus provides 6. a heat exchanger having structural continuity and high thermal efliciency.

Although I have described in detail the preferred method of my invention, I contemplate that changes may be made without departing from the scope or spirit of my invention and I desire to be limited only by the claims.

I claim:

1. In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between |first and second heat exchanger fluids flowing in said first and second passageways therethrough respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing within said second passageway a spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufficiently high to allow brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said spacer member; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; collapsing said spacer member and withdrawing said member from said second passageway.

2. In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wail comprising the steps of: providing within said second passageway a spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufliciently high to allow brazing alloy to flow between said packing and said common wall; supportingsaid common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said spacer member; cooling said exchanger thereby solidfying said brazing alloy in bonding relation with said common wall and said packing; collapsing said spacer member and withdrawing said member from one of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

3. In the construction of a brazedplate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways therethrough respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing within said second passageway a spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufficiently high to allow said brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in'contiguous relation with said packing during the heating step via forces exerted by said spacer member; isolating said spacer member for said brazing alloy to avoid bonding with said spacer member; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; collapsing of said spacer member and withdrawing said member from; one of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

4. In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways therethrough respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing within said second passageway 'a corrugated spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufiiciently high to allow brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said spacer member; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; progressively collapsing undulations of said corrugated'spacer member and withdrawing said member from said second passageway.

5.In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrou-gh between first and second heat exchange fluids flowing in said first and second passageways respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing within said second passageway a corrugated spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufficiently high to allow brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said spacer member; isolating said spacer member from said brazing alloy to avoid bonding with said spacer member; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; progressively collapsing undulations of said corrugated spacer member and withdrawing said member from one, of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

6. In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways respectively, wherein only thefirst of said first and second passageways contains a heat transfer packing extending from said common'wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of: providing a sheet of porous material;

55 forming a corrugated spacer member by corrugating said porous material with undulations of a form having crests which define edges; providing within said second passageway said corrugated spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; immersing said exchanger in a bath of molten salt and heating said exchanger in said salt bath to a temperature sufficiently high to allow said brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said edges of said spacer member; isolating said spacer member from said brazing alloy to avoid bonding with said spacer member; withdrawing said exchanger from said salt bath; draining molten salt from said second passageway through the pores of said spacer; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; progressively collapsing undulations of said corrugated spaced member and withdrawing said member from one of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

7. In the construction of a brazed plate type heat exchanger having first and second passageways disposed on opposite sides of a common wall for exchanging heat therethrough between first and second heat exchange fluids flowing in said first and second passageways respectively, wherein only the first of said first and second passageways contains a heat transfer packing extending from said common wall to the opposite wall of said first passageway, the method of establishing a highly thermal conducting union between said packing and said common wall comprising the steps of forming a corrugated spacer member by corrugating a sheet of material with undulations of a form having crests which define edges; providing within said second passageway said corrugated spacer member extending from said common wall in spacing relation to the opposite wall of said second passageway; providing a brazing alloy between said packing and said common wall; heating said exchanger to a temperature sufficiently high to allow said brazing alloy to flow between said packing and said common wall; supporting said common wall inwardly of the margins thereof in contiguous relation with said packing during the heating step via forces exerted by said edges of said space-r member; isolating said spacer member from said brazing alloy to avoid bonding with said spacer member; cooling said exchanger thereby solidifying said brazing alloy in bonding relation with said common wall and said packing; progressively collapsing undulations of said corrugated spacer member and withdrawing said member from one of the openings provided for passage of said second heat exchange fluid to and from said second passageway.

8. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing said assemblage of elements with spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said spacer members; providing means to preventsaid brazing alloy from bonding said 9 spacer member to said plates; heating said assemblage of elements to a temperature sufiiciently high to melt said brazing alloy; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and withdrawing said spacer members from said assemblage of elements.

9. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; forming collapsible spacer members; providing said assemblage of elements with spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said spacer members; proving means to prevent said brazing alloy from bonding said spacer members to said plates; heating said assemblage of elements to a temperature sufficiently high to melt said brazing alloy; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and collapsing the spacer members and withdrawing said spacer members from said assemblage of elements.

10. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing sheets of material; forming corrugated spacer members by corrugating said material; providing said assemblage of elements with corrugated spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said spacer members; providing means to pre vent said brazing alloy from bonding said spacer members to said plates; heating said assemblage of elements to a temperature sufliciently high to melt said brazing alloy; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and progressively collapsing the undulations of said corrugated spacer members and withdrawing said spacer members from said assemblage of elements.

11. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing sheets of material; forming corrugated spacer members by corrugating said material with undulations of a form having crests which define edges; providing said assemblage of elements with corrguated spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said edges of said spacer members; providing means to prevent said brazing alloy from bonding said spacer members to said plates; heating said assemblage of elements to a temperature sufiiciently high to melt said brazing alloy; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates and progressively collapsing the undulations of said corrugated spacer members and withdrawing said spacer members from said assemblage of elements.

12. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing sheets of materials; forming corrugated spacer members by corrugating said material with undulations of a form having crests which define edges; providing said assemblage of elements with corrugated spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said edges of said spacer members; providing means to prevent said brazing alloy from bonding said spacer members to said plates; heating said assemblage of elements to a temperature sufliciently high to melt said brazing alloy; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and progressively collapsing the undulations of said corrugated spacer members and withdrawing said spacer members from said assemblageof elements through said openings.

13. A method of constructing a brazed plate type heat exchanger having heat transfer packing in certain of the passageways thereof comprising the steps of: forming an assemblage of elements including a plurality of metallic plates of similar configuration arranged in superposed spaced generally parallel relationship defining the side walls of a plurality of first and second passageways for passage of first and second heat exchange media respectively, means for interconnecting adjacent plates at the margins thereof thereby defining in conjunction with said plates said plurality of passageways, means defining inlet and outlet openings for said passageways, heat transfer packing extending from one plate to the other plate in the first of said passageways, and a brazing alloy disposed for bonding said packing to said plates adjacent thereto; providing sheets of porous material; forming corruga-ted spacer members by corrugating said porous material with undulations of a form having crests which define edges; providing said assemblage of elements with corrugated spacer members within the second passageways thereof; supporting the plates defining the side walls of said second passageways by said edges of said spacer members; providing means to prevent said brazing alloy from bonding said spacer members to said plates; im-

mersing said assemblage of elements in a bath of molten salt; heating said assemblage of elements in said bath to a temperature sufliciently high to melt said brazing alloy; Withdrawing said assemblage of elements from said bath; draining molten salt from said second passageways through the pores of said spacer members; cooling said assemblage of elements to solidify said brazing alloy thereby bonding said packing to said plates; and progressively collapsing the undulations of said corrugated spacer members and Withdrawing said spacer members from said assemblage of elements through said openings.

References Cited UNITED STATES PATENTS Wellman 29-4723 Brown et al. 29-423 X Jaffee 29423 Valyi 29423 X Staufier 29455 JOHN F. CAMPBELL, Primary Examiner.

PAUL M. COHEN, Assistant Examiner. 

1. IN THE COMBINATION OF A BRAZED PLATE TYPE HEAT EXCHANGER HAVING FIRST AND SECOND PASSAGEWAYS DISPOSED ON OPPOSITE SIDES OF A COMMON WALL FOR EXCHANGING HEAT THERETHROUGH BETWEEN FIRST AND SECOND HEAT EXCHANGER FLUIDS FLOWING IN SAID FIRST AND SECOND PASSAGEWAYS THERETHROUGH RESPECTIVELY, WHEREIN ONLY THE FIRST OF SAID FIRST AND SECOND PASSAGEWAYS CONTAINS A HEAT TRANSFER PACKING EXTENDING FROM SAID COMMON WALL TO THE OPPOSITE WALL OF SAID FIRST PASSAGEWAY, THE METHOD OF ESTABLISHING A HIGHLY THERMAL CONDUCTING UNION BETWEEN SAID PACKING AND SAID COMMON WALL COMPRISING THE STEPS OF: PROVIDING WITHIN SAID SECOND PASSAGEWAY A SPACER MEMBER EXTENDING FROM SAID COMMON WALL IN SPACING RELATION TO THE OPPOSITE WALL OF SAID SECOND PASSAGEWAY; PROVIDING A BRAZING ALLOY BETWEEN SAID PACKING AND SAID COMMON WALL; HEATING SAID EXCHANGER TO A TEMPERATURE SUFFICIENTLY HIGH TO ALLOW BRAZING ALLOY TO FLOW BETWEEN SAID PACKING AND SAID COMMON WALL; SUPPORTING SAID COMMON WALL INWARDLY OF THE MARGINS THEREOF IN CONTIGUOUS RELATION WITH SAID PACKING DURING THE HEATING STEP VIA FORCES EXERTED BY SAID SPACER MEMBER; COOLING SAID EXCHANGER THEREBY SOLIDIFYING SAID BRAZING ALLOY IN BONDING RELATION WITH SAID COMMON WALL AND SAID PACKING; COLLAPSING SAID SPACER MEMBER AND WITHDRAWING SAID MEMBER FROM SAID SECOND PASSAGEWAY. 